Among various semiconductor devices, power devices for the high-power control that are used to control electric vehicles, electric automobiles or the like, generate a large amount of heat. Thus, a power module substrate in which a metal plate having excellent conductivity and being served as a circuit layer is bonded on a ceramic substrate (insulation layer) composed of, for example, AlN (aluminum nitride) or the like, is conventionally widely used as a substrate for mounting the power devices.
A semiconductor device as a power device is mounted on the circuit layer of the power module substrate mentioned above via a solder material, and a power module is produced. As a power module substrate of this type, a power module substrate having a structure in which a heatsink having an excellent thermal conductivity is also bonded to a lower surface of the ceramic substrate in order to dissipate the heat caused by the semiconductor device and the heat is configured to be dissipated is known.
Al (aluminum), Cu (copper) or the like, is used as a metal making the circuit layer. For example, in Patent Document 1, a power module substrate in which a circuit layer composed of an aluminum plate is bonded to a surface of a ceramic substrate is proposed.
In addition, in Patent Document 2, a power module substrate in which a circuit layer composed of a copper plate is bonded to a surface of a ceramic substrate is proposed.